The present invention relates generally to television broadcast systems, and more particularly to analog or digital television broadcast receivers and methods wherein program content rating data transmitted concurrently with a television program signal is utilized to provide parental control over the viewing by children of television programs broadcast over the system.
Various systems and receivers have been proposed for conveying program rating data along with a conventional NTSC television transmission. In particular, U.S. Pat. No. 4,554,584 to Carl Elam et al. describes a system wherein program content rating data is transmitted as digital codes along with conventional closed captioning data as part of a data component on line 21 in the vertical blanking interval. A receiver is described wherein this information is compared with stored user-selected program limits or viewing authorizations and the program is selectively blanked if it is not authorized by the stored selection criteria.
One problem which may arise in the implementation of the system described in U.S. Pat. No. 4,554,584 is that in certain cases the received television program signal may be so weak or degraded by interference as to prevent the decoding of reliable closed captioning data or program content rating data. Under the latter circumstance, the receiver may ultimately provide access to an unauthorized program, or deny access to an authorized program. Furthermore, a signal weakened or degraded by normal interference could cause temporary loss of rating data while the system rejects such unreliable data. In turn, intermittent blanking of the program may be introduced which would create a nuisance for the viewer. This is particularly the case when the logic is such that the program will be blanked in the absence of receipt of a program ratings code. For example, the parental control afforded by the receiver of the Elam et al. patent could potentially be defeated by a viewer weakening the television program signal sufficiently, as by disconnecting a portion of the antenna, so that reliable program content rating characters in a received, unauthorized program are not derived by the receiver for comparison with the stored viewing authorizations and the receiver defaults to a viewing enabled state.
The present invention is directed to an improvement in the system proposed by Elam et al. wherein in an analog or digital television receiver the integrity of a data signal transmitted with the television program transmission is monitored to determine whether the data signal is being reliably received, and hence whether reliable rating characters are being received. In the event the integrity of the data signal falls below an acceptable threshold level, the program is either blanked, or, depending on the operating mode of the receiver, a determination is made whether to blank depending on either 1) the viewing authorization then in effect for the viewer, or 2) whether a default to view or default to blank authorization has been stored for the viewer.
Accordingly, it is a general object of the present invention to provide a television receiver which-provides conditional access to received television programs.
It is a more specific object of the present invention to provide an analog or digital television receiver which provides conditional access to received television programs depending on the presence of reliable rating data in the received program signal.
It is a more specific object of the present invention to provide an analog or digital television receiver which provides conditional access to received television programs depending on the presence of reliable rating data in the received program signal and on the applicable viewer authorization then in effect.
It is a still more specific object of the present invention to provide an analog or digital television receiver wherein the presence of reliable program rating data is confirmed by monitoring parity error rate in a data signal component of the received television broadcast signal.